| Considering the problems of the air source heat pump system in the cold region during winter heating such as poor performance,easy to frost,this paper studies a small solar-air dual source heat pump system suitable foe rural construction to replace the domestic coal-fired heating stove.This paper expounds the operating principle and switching mode of the system,simulates the operation of the system in different environments,and calculates the economic advantages and energy saving and environmental benefits of the system.The dual source heat pump system studied in this paper is composed of an air source heat pump(cold)hot water unit and a small solar hot water system.A heat exchange coil is placed inside the heat storage tank,and connected in parallel with the outdoor air-cooled evaporator by an electric three-way valve,as a water source evaporator for heating in winter to use the heat of low-temperature hot water inside the storage tank.According to the changes of the outdoor environment temperature,the system can automatically select the operating mode(water or air source operating mode).The system can compensate the air source heat pump heating problems to some extent when the outdoor air temperature is low.At the same time,reasonable and effective use of solar radiation energy,maximize the use of renewable energy.In this paper,a mathematical model of the solar-air dual source heat pump system and its components is established,and a rural residential building is selected to determine the capacity of each part of the system according to the design thermal load of the building.At the same time,the time when the system is switched from the water source operation mode to the air source operation mode is defined as the switching time,and the corresponding ambient temperature is the switching temperature.It introduces the concept of heating seasonal performance factor(HSPF),based on the maximum HSPF,the optimum switching temperature and the optimum switching time are determined.And the solar collector area and the volume of heat storage water tank are obtained according to the outdoor weather parameters in January in Beijing.This paper simulates the heating performance of the system when it operates in air and water mode respectively through the established mathematical model of the system.Simulate the change of the heat storage water temperature under different switching time according to the required area of the solar collector area and the volume of heat storage water tank.Considering the system heating COP is related to solar irradiation parameters,based on the outdoor weather parameters in winter in Beijing,the heating COP of the system at different switching time and switching temperature is calculated.From the perspective of obtaining the maximum heating COP,determine the optimum switching temperature and the optimum switching time.Analyze the change of heat storage water temperature and heating COP in different collector area,volume of heat storage water tank and switching time.Analyze the energy conservation and thermal comfort of floor radiation coil,radiator and fan coil using exergy analysis method,so as to explain the rationality of floor radiation coil.Finally,this paper calculates the initial investment and annual operating cost of solar-air dual source heat pump system with different collector area and heat storage water tank capacity at different switching time,and determines the optimum economy switching temperature and time of the system from the perspective of improving system economy.The initial investment,annual operating cost and annual cost of the system's optimum economy switching temperature and time are compared with the domestic coal-fired heating stove and gas-fired hot water heating installation,at the same time,the energy conservation and environmental protection of the design system of this paper is expounded,and the superiority of the system is proved. |
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